Ricoh B889 Manual page 33

Types of Folding - 2/2
Types C and D are adjusted folds.
This ensures that the surfaces at the top and bottom of the stack
are always the longest, with smaller folds hidden inside the stack.
Type A long folds do not ensure this, and some customers might
think that is untidy.
In adjusted folds, the machine adjusts the positions of the smaller
folds, to make sure that the top and bottom folds have the required
length.
The machine adjusts the fold widths automatically, based on
original length, copy length, number of folds, and type of folding
selected.
Slide 33
Type C is a long fold, and type D is a file fold. But the folded edges are not
aligned (the fold surfaces do not all have the same lengths).
33
B889 - Fan Fold Unit